Packing carryover

As with any analytical instrumentation that incorporates an autosampler, it is essential to evaluate the percent carryover obtained for a particular analyte under particular rinsing conditions. For these evaluations, a cartridge packed with a C18 stationary phase (80 x 0.5 mm/column) was employed. Gradient and detection conditions were the same as those described for the evaluation of retention time and peak area reproducibility (see Section 6.3.2). 

For the absorption of soluble gases or particulates from the gas streams, scrubbers can be used. These are generally simple packed columns, spray towers, or Venturi units. Design methods are well established [236]. Attention must be paid to the prevention of sprays, mists, and carryover when wet scrubbers are used. 

There are many advantages (but also some disadvantages) of using particles dispersed in the electrolyte as pseudostationary phase. There is no particle packing procedure needed. Frits are not used. The solid phase is always refreshed so that carryover from complex samples is no problem. 

In packed bed reactors the solid catalyst is held stationary by plates at the top and bottom of the bed. In contrast, in fluidized bed reactors, the catalyst bed is relatively loosely packed, and there is no plate at the top. Rapid fluid flow from the bottom raises the bed and ensures good mixing, leading to insignificant temperature or concentration gradients. However, due to high fluid velocity some catalyst carryover is common. 

Problem A packed column was designed to strip methanol and water from ethylene glycol. When all the methanol and water were stripped out of the glycol, excessive glycol carryover occurred. 

Absorption takes place in either staged or plate towers or continuous or packed contactor. However, in both cases the flow is continuous. In the ideal equilibrium stage model, two phases are contacted, well mixed, come to equilibrium, and then are separated with no carryover. Real processes are evaluated by expressing efficiency as a percentage of the change that would occur in the ideal stages. Any liquid carryover is removed by mechanical means. 

The durability of SPC structures in aggressive environments depends on the diffusion rate of chemically active reagents into a material. Fluid penetration is realized through imperfections in molecular packing of the binder and it is accelerated at an increase of temperature and pressure. In this connection, definition of a diffusion coefficient (as a key parameter of a liquid carryover) becomes the important problem. 

To conclude, the FIA response curve obtained in such a system, which conforms to the tanks-in-series model, reflects the reaction rate at which the detected species is formed—or consumed—and on the physical parameters of the system. The RTD curve, however, in analogy with what applies to tubular and packed reactors, is the function of the physical parameters alone. Thus even if the response curve is narrower than the RTD curves obtained by the tracer experiment, it is of no use to try to reach the thus seemingly achievable higher sampling frequency, since the reactant—or lack of reagent persisting in the chamber—will result in carryover and in loss of reproducibility. 

Bed limiters should always be specified for plastic packings. Because of their light weight, pieces of plastic packing are extremely easy to fluidize and carry over, and often cause problems in condensers or downstream equipment. The author has experienced extensive carryover of plastic packing from towers that did not have bed limiters. Others (74,144, 320) also share the above recommendation. 

Foaming in fractionation and absorption columns can drastically lower capacity and lead to premature flooding, liquid carryover, and solvent losses. In packed columns, foaming can also lead to poor distributor and redistributor action. 

Cas-liquid-solid packed column bio reactor Carryover [foaming]. ... 

Manual injectors are operationally qualified for repeatability and carryover. Autosamplers are additionally checked for accuracy. Injection systems are qualified after the solvent dehvery system and the detector. To eliminate subjective effects, the chromatographic column is excluded from the setup for qualifying injectors. The column is replaced by a low internal diameter, significant length stainless steel tubing, generating a pressure drop similar to that in a packed column (about 100 bar). 

Caustic strength Organic carryover Precipitation Packing failure... 

This automated SPE flow system presents two major drawbacks. First, for an inexperienced operator, manual packing of the SPE column is not an easy task and prone to introduce low reprodudbihty into the methodology. Second, the same sorbent column is used for diflerent samples, increasing the risk of crosscontamination and carryover. Therefore, sorbent washing with 3 mL of hexane is recommended for every 30 samples analyzed. 

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